This invention relates generally to decontamination of water, and more particularly, to a method for removing heavy metals and actinides from contaminated water using a magnetic polymer resin, a method for preparation of the resin, the resin itself, and a method for regenerating and reusing the magnetic polymer resin.
Wastes generated by government and industry as a result of the nuclear fuel cycle, nuclear weapons development and production and other industrial processes commonly include water contaminated with various heavy metals and radioactive materials including measurable amounts of actinides. Water decontamination methods available presently fall into two basic types: 1) maximum dilution, and 2) maximum concentration and subsequent removal of the contaminant. Maximum dilution achieves decontamination by dramatically increasing the amount of otherwise inert materials in a contaminated water sample and effectively decreasing contaminant concentration prior to either storage or disposal by release into the environment. Maximum concentration and removal, on the other hand, typically involves water purification methods including adsorption, ion exchange, chemical precipitation, flocculation, filtration and biological retention. Such purification methods allow for the concentration and removal of contaminants in order that the contaminants may be stored or disposed of in isolated hazardous waste repositories. Varieties of these methods have been used in managing radioactive wastes, nonradioactive wastes and mixed wastes. The present invention involves concentration and removal of contaminants.
It has been demonstrated that mixed valence iron oxide compounds, or ferrites, are effective in removing heavy metals and suspended solids from aqueous media. Due to their unique chemical structure, ferrites may contain one or more iron atoms capable of being replaced by other metal ions. This characteristic, together with ferrites' strongly magnetic character, make them particularly suited to applications associated with waste water decontamination. Toshio Takada, "Removal of Heavy Metal Ions from Waste Water by Ferritization," Koga to Taisaku 13, 37 (1977); Toshiyuki Iguchi, Toyokazu Kamura, and Masahiro Inoue, "Ferrite Process for Treatment of Waste Water Containing Heavy Metals," Poll. Prev. and Dev. Tech. 10, 49 (1979); Tomio Nagashima, "Removal of Hazardous Metals from Waste Water," Japan, Kokai 77 77,465 (1977); Masakatu Sano, "Removal of Hazardous Metals from Waste Water," Japan, Kokai 77 67,156 (1977); Izuru Sugano, "Removal of Hazardous Metals from Waste Water," Japan, Kokai 77 67,154 (1977); Christopher de Latour and Henry Kolm, "Magnetic Separation in Waste Water Pollution Control," IEEE Trans. on Magnetics 11, 1570 (1975). Magnetite, a common ferrite, is a strong adsorbent which has been used successfully for removing organic materials and biological matter such as algae, bacteria, viruses, and seeds from water. Thomas E. Boyd, M. J. Cusick, and James D. Navratil, "Ferrite Separation Science and Technology," Recent Developments in Separation Science, 8, pp. 207-232, N. N. Li and J. D. Navratil, Eds., CRC Press, 1986.
Ferrites have also been demonstrated to be effective in removal of actinides (thorium, uranium, plutonium and americium) from waste water generated at the nation's nuclear weapons production facilities. Ferrite removal of actinides can be accomplished using several different techniques including mixing prepared ferrites with aqueous wastes and preparing ferrites in situ in waste solutions. "Removal of Radioactive Materials from Waste Solutions Via Magnetic Ferrites," Thomas E. Boyd, Robert L. Kochen, and Marlene Y. Price, ANS Topical Meeting on Treatment and Handling of Radioactive Wastes, Richland, Wash. (1982); Robert. L. Kochen, "Actinide Removal From Aqueous Solution with Activated Magnetite," RFP-4100, Rockwell International, Rocky Flats Plant, Golden, Colo. (1987); Thomas E. Boyd, Robert L. Kochen, "Ferrite Treatment of Actinide Waste Solutions: Continuous Processing of Rocky Flats Process Waste," RFP-3476, Rockwell International, Rocky Flats Plant, Golden, Colo. (1983), Thomas E. Boyd, Robert L. Kochen, James D. Navratil and Marlene Y. Price, "Actinide Aqueous Waste Treatment Studies Using Ferrites," Radioactive Waste Management and the Nuclear Fuel Cycle, 4(2), 1983.
A different approach to waste water decontamination involves the use of anion exchange resins for the removal of various contaminants from aqueous media. Polyamine-epichlorohydrin-type resins were first demonstrated to be effective weakly basic anion exchange resins approximately thirty years ago. C. A. Feldt and G. T. Kekish, "Weakly Basic Anion Exchange Resins," U.S. Pat. No. 3,092,617 (1963). Organic ion exchange resins are commonly used in chemical treatment of contaminated water in both industrial waste water treatment and general water resources engineering. Extensive research efforts have been made to develop organic ion exchange resins that are suited to adsorbing particular organic and inorganic contaminants. Alone, however, organic ion exchange resins are not especially effective for purposes of removing actinides from water, especially since noncharged polymeric species can be present in the water.
Due to the fact that large amounts of waste water containing heavy metals, or actinides, or both, are being generated, stored and disposed of in the United States and elsewhere, improved methods for handling and decontaminating such waste water are needed. The present invention helps to serve this need by providing a highly effective means for removing heavy metals and actinides from water.